Inert non-adsorbing crimpable capillaries and devices for adjusting gas flow in isotope ratio analysis

Abstract

A gas transfer system for transferring gas into an analytical instrument for isotope ratio analysis comprises a capillary for delivering sample and/or reference gas from a gas source, a first connector for connecting the capillary to the gas source, a second connector for connecting the capillary to the analytical instrument, a crimping device, wherein the internal surface of the capillary comprises a coating material to prevent or minimize adsorption of water to the surface. Also provided is a device for regulating gas flow in a gas inlet system of an analytical instrument, comprising a body member having an internal gas flow channel, and a clamping member for attachment to the body member such that when the clamping member is tightened onto the body member, the internal gas flow channel is adjustably and reversibly crimped, to adjust gas flow therethrough.

What is claimed is: 
     
       1. A method of reducing isotope scrambling during isotope ratio analysis of a gas from a sample that comprises clumped isotopes, comprising:
 transmitting the sample gas from at least one gas source through a first capillary into a mass spectrometer and performing a first isotopic measurement, at least a portion of the first capillary comprising a coating material to prevent or minimize adsorption of water to a surface of the first capillary, the coating material free of metal ions that could cause isotope scrambling of clumped isotopes; 
 providing at least one reference gas from another reservoir; and 
 transmitting the at least one reference gas through a second capillary into the mass spectrometer and performing a second isotopic measurement, 
 wherein gas flow into the mass spectrometer is adjusted by crimping the first capillary or the second capillary for the first or second isotopic measurements to obtain substantially equal gas flow during measurements of reference gas and sample gas. 
 
     
     
       2. The method of  claim 1 , wherein the first capillary or second capillary includes a crimpable stainless steel, metal or alloy capillary. 
     
     
       3. The method of  claim 1 , wherein the first capillary or second capillary includes a non-crimpable glass, silica, or ceramic capillary. 
     
     
       4. The method of  claim 1 , wherein said at least one gas source is a gas source with an adjustable volume. 
     
     
       5. The method of  claim 1 , wherein said reference gas is selected from carbon monoxide, carbon dioxide, hydrogen, nitrogen, nitrogen oxides, and sulfur dioxide. 
     
     
       6. The method of  claim 1 , wherein said at least one gas source is selected from the group consisting of a microvolume tube, an adjustable gas bellows system, a syringe and a gas bottle. 
     
     
       7. The method of  claim 6 , wherein the microvolume tube is a microvolume CaCO3 decomposition tube. 
     
     
       8. The method of  claim 1 , wherein crimping the first capillary includes crimping at a section where an inner diameter of the first capillary is in a range from about 100 to about 800 micrometres, in a range from about 200 to about 600 micrometres, in a range from about 200 to about 500 micrometres, or in a range from about 200 to about 400 micrometres. 
     
     
       9. The method of  claim 8 , wherein the section of the first capillary is a narrower section, the first capillary having the narrower section and a wider section with a second, larger diameter than the first diameter, the narrower section including the coating. 
     
     
       10. The method of  claim 9 , wherein the second, larger diameter of the wider section is in a range from about 300 micrometres to about 2 millimetres, in a range from about 500 micrometres to about 2 millimetres, in a range from about 300 micrometres to about 1.5 millimetres, in a range from about 500 micrometres to about 1.5 millimetres, in a range from about 300 micrometres to about 1 millimetre, or in a range from about 500 micrometres to about 1 millimetre.